Smog Tests

Soft Cars said:
Lesson learned: Don't unhook your battery if you're going to get your car smogged anytime soon. That's what I did last week when I replaced the front valve cover gasket. The service manual said "disconnect battery" as the very first step. I went ahead and did that so as to not put the computer at risk while doing repairs. So now I have to put the car into an unknown number of drive cycles before the car will be ready for a smog test. The smog tech said the computer needs time to build a history from the reports it receives from the post catalytic oxygen sensor. Right now I'm left wondering if some kind of scanner would've told me whether or not the car was ready for testing. $39.75 out the window.
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I saw this alot when I was an emissions Inspector. Some vehicle are easy to reset. Most hondas say to drive 200 miles. Some like a Ford Escape are a 12 step and very specific to reset .
 
Even after driving the car up and down the freeway all week, all the monitors check out except the HTR monitor which always has a red X next to it on the I/M Readiness checklist. What if it's never ready? They'll have to go ahead and fail the test correct? I'm supposed to have this done by 02/08/2023.
 
clinebarger said:
What State & County is the car registered? Texas emissions testing counties allow ONE "not ready" on 2001 & up OBD2 vehicles.
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The car is registered in California. They are not going to let me buy 2023 tags unless all the monitors have green checkmarks.

Where is the oxygen sensor heater monitor? Is the oxygen sensor - the monitor itself?

The car only has two oxygen sensors. One on the rear exhaust manifold, and one downstream immediately after the catalytic converter.
 
Bladecutter said:
Have you Googled your car's drive cycle process, and followed it yet?
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Yes I did that last night when the freeways were less busy. They said to drive 55 steadily for three minutes and then coast down to 20. I did that several times.
 
Some years ago, I did the same thing that the OP did. Disconnected the battery for some work, shortly before going for safety and emissions inspection. It was on a 2001 Altima that I had since new. On the scan it indicated that 2 systems were "not ready for testing". The tech told me that if had been a 2000 model, then 2 "not readys" were acceptable. But a 2001 could only have one. This was in PA. where they had adopted California new car emissions for the 2001 models. After I took it for a couple higher speed runs on a local bypass, plus the tech letting it idle for some time, it passed.
 
There are a number of conditions that have to be met to set the O2 sensor heater circuit. It's more than just the 55mph with deacceleration runs. Prior to that you have to idle under high electrical load (rear defroster, headlights, AC, etc.) for 2.5 minutes. Google the GM ecm monitor drive cycle. The GM cycle has worked for all cars I've tried it on. Some have taken a couple of complete cycles, none have required 3 yet.
The drive 55 with deceleration is the toughest. I always fudge it on the high side (60-65) so I don't get run over. Hasn't been a problem. For deacel, pulling into the right wide shoulder/breakdown lane on a freeway with light traffic with the flashers on is the safest way (for me), but the debris can be rough on tires.
In Nevada and for Federal, the Evap can be in a not ready state and still pass. Evap in a fail state, the smog test will fail.
 
Soft Cars said:
The car is registered in California. They are not going to let me buy 2023 tags unless all the monitors have green checkmarks.

Where is the oxygen sensor heater monitor? Is the oxygen sensor - the monitor itself?

The car only has two oxygen sensors. One on the rear exhaust manifold, and one downstream immediately after the catalytic converter.
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I believe you are allowed the EVAP monitor to be not ready in California? Not that it helps you.

The PCM monitors how fast the O2 Sensors start switching....The heating element in the O2 Sensors allows the sensor to heat up faster than just allowing exhaust heat to warm the sensor naturally. A sensor that fails to switch in a allotted time will flag a failure in the PCM....If it's a 2-trip failure to set a DTC.....A DTC will not set unless the same failure happens again on the same trip.

A single failure per trip won't set DTC's.....But can keep the O2 Heater Monitor from completing. Having exhaust leaks that close up after the engine is warmed up can cause such an issue....As can a weak heater in one of the O2's.

All this highway driving isn't helping, I find cold starts help complete the O2 Heater Monitor Complete more than anything.
 
clinebarger said:
I believe you are allowed the EVAP monitor to be not ready in California? Not that it helps you.

The PCM monitors how fast the O2 Sensors start switching....The heating element in the O2 Sensors allows the sensor to heat up faster than just allowing exhaust heat to warm the sensor naturally. A sensor that fails to switch in a allotted time will flag a failure in the PCM....If it's a 2-trip failure to set a DTC.....A DTC will not set unless the same failure happens again on the same trip.

A single failure per trip won't set DTC's.....But can keep the O2 Heater Monitor from completing. Having exhaust leaks that close up after the engine is warmed up can cause such an issue....As can a weak heater in one of the O2's.

All this highway driving isn't helping, I find cold starts help complete the O2 Heater Monitor Complete more than anything.
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Is the PCM the monitor, or are the oxygen sensors the monitor? It would make more sence for the PCM to be the monitor since it's supposed to monitor stuff. I tried a cold start this morning and let the car sit there and idle for 15 minutes with the fan and rear defroster on. Red X on the scan tool won't budge. I'm now beginning to think there's something wrong with the downstream O2 sensor since it's the one still original.
 
clinebarger said:
The PCM is monitoring the O2's.....Heater Circuit Integrity & Heater Performance.
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Ok good, that makes sense. On the scan tool today, the downstream O2 stayed at -417 and didn't fluctuate at all. If I remember correctly, O2 sensors are supposed to fluctuate.
 
KrisZ said:
If you drive it for 50-100 miles everything should be ready for the test.
I also thought that if you got “not ready” during the test and paid for it, the next test should be free. Maybe that’s dependent on a testing place?
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I don't think it's just a specific number of miles but also a number of minimum startups and driving under various conditions.
 
vavavroom said:
I don't think it's just a specific number of miles but also a number of minimum startups.
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Is the actual drive cycle procedure in the service manual? I have the two volume GM service manual, but can't find the drive cycle procedure in it anywhere. The scan tool says to refer to the service manual for the drive cycle procedure.
 
Soft Cars said:
Is the actual drive cycle procedure in the service manual? I have the two volume GM service manual, but can't find the drive cycle procedure in it anywhere. The scan tool says to refer to the service manual for the drive cycle procedure.
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It's not specified in any of my manuals. I'd make sure to drive the vehicles in the city and on the freeway for a few days and ideally over 100 miles. I don't know if a dozen start ups is sufficient. I believe you need some coasting from 60 mph to near 0 mph in there. Vehicles;es really should have a readiness idiot light that goes eventually out after a battery disconnect. I won't go for a smog test if I have disconnected the battery just a few days ago.
 
Soft Cars said:
Ok good, that makes sense. On the scan tool today, the downstream O2 stayed at -417 and didn't fluctuate at all. If I remember correctly, O2 sensors are supposed to fluctuate.
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The Bias Voltage on GM vehicles is @ 450mV.....I'd consider a static 417mV close enough to maybe suspect a bad sensor or a open circuit.

Don't trust scan tool data unless it's "Known Good".....Especially true for generic OBD scan tools.
 
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